[Mac] Enable MacViews bookmark editor behind --enable-mac-views-dialogs.

components/constrained_window/constrained_window_views.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/constrained_window/constrained_window_views.h"
 
 #include <algorithm>
 
 #include "components/constrained_window/constrained_window_views_client.h"
 #include "components/guest_view/browser/guest_view_base.h"
@@ skipping 148 matching lines @@
                                              gfx::NativeWindow parent) {
   DCHECK_NE(ui::MODAL_TYPE_CHILD, dialog->GetModalType());
   DCHECK_NE(ui::MODAL_TYPE_NONE, dialog->GetModalType());
 
   DCHECK(constrained_window_views_client);
   gfx::NativeView parent_view =
       parent ? constrained_window_views_client->GetDialogHostView(parent)
              : nullptr;
   views::Widget* widget =
       views::DialogDelegate::CreateDialogWidget(dialog, NULL, parent_view);
-  if (!dialog->UseNewStyleForThisDialog())
+
+  bool requires_positioning = dialog->UseNewStyleForThisDialog();
+
+#if defined(OS_MACOSX)
+  // On Mac, window modal dialogs are displayed as sheets, so their position is
+  // managed by the parent window.
+  requires_positioning = false;
+#endif
+
+  if (!requires_positioning)
     return widget;
+
   ModalDialogHost* host = constrained_window_views_client->
       GetModalDialogHost(parent);
   if (host) {
     DCHECK_EQ(parent_view, host->GetHostView());
     ModalDialogHostObserver* dialog_host_observer =
         new WidgetModalDialogHostObserverViews(
             host, widget, kWidgetModalDialogHostObserverViewsKey);
     dialog_host_observer->OnPositionRequiresUpdate();
   }
   return widget;
 }
 
 }  // namespace constrained window